U.S. Pat. Nos. 4,768,347 and 4,805,416, both assigned to the assignee hereof, disclose refrigerant handling systems that include a compressor having an inlet coupled to a refrigerant source, such as refrigeration equipment from which refrigerant is to be recovered, and an outlet coupled through a condenser to a refrigerant storage container. It is required by SAE standards that oil contamination in refrigerant pumped into the storage container for later purification and reuse be limited to less than 4,000 ppm. ASHRAE and ARI standards are similar but more stringent. It is therefore desirable not only to remove oil from refrigerant at the compressor outlet, but also to return this oil to the compressor sump to avoid or minimize service addition of oil to the compressor sump or repair of damage to the compressor due to lack of proper lubrication.
It has heretofore been proposed to employ a metal canister having an open internal volume coupled to the compressor outlet so that refrigerant vapor loses velocity within the canister and oil droplets fall by gravity to the lower portion of the canister. However, hot refrigerant vapor from the compressor outlet, contacting the cooler metal wall of the canister, causes condensation of refrigerant and interferes with proper oil separation. Typically, the oil separator has therefore been provided with a blanket heater to heat the canister walls in an effort to avoid refrigerant condensation within the canister. A float valve at the lower portion of the canister returns collected oil to the compressor inlet.
It is also been found desirable, upon termination of compressor operation, to bleed refrigerant from the compressor outlet or discharge line to the compressor inlet or suction line in order to pressurize the system oil separator at the compressor inlet, to provide for proper draining of collected oil, and also to ease subsequent starting of the compressor. However, it is necessary to limit the amount of refrigerant bled to the low-pressure side of the compressor to avoid condensation of refrigerant and prevent "slugging" upon subsequent compressor operation.
It is therefore a general object of the present invention to provide a compressor oil separation system that finds particular utility in refrigerant handling systems such as refrigerant recovery, purification and recharging systems of the character disclosed in the aforementioned patents, that addresses the aforementioned needs and deficiencies of prior art systems, that is economical to manufacture, that provides reliable service over an extended operating lifetime, and in which the compressor oil separator contains no moving parts. In this connection, it is a more specific object of the invention to provide a compressor oil separator that eliminates the need for the electric heater blanket heretofore employed in the art to prevent condensation of refrigerant in the oil separator, with consequent reduction in assembly and operating costs.